Dynamic random access memory (DRAM) is a type of memory in which the data stored in the memory must periodically be refreshed to avoid loss of the data. A common form of DRAM stores data using capacitors. The capacitor may be placed in either a discharged state or a charged state to represent bit values of zero or one. Since capacitors leak charge over time, the data stored using capacitors will fade unless the capacitor is refreshed periodically.
In the present application, the terms “dynamic random access memory” and “DRAM” are used to refer to any kind of memory which requires its data to be refreshed periodically to avoid loss of the data (whether the data is stored using capacitors or using another kind of storage element).
DRAM is increasingly being used for storage of secure data and secure program code. This is particularly the case in systems in which the DRAM is integrated into the same system-on-chip or package as the processing logic associated with the DRAM. For example, 3D-integrated DRAMs may be used in a system-on-chip having multiple stacked layers. By isolating the DRAM from the external world, it is more difficult for an attacker to probe the interface between the DRAM and the processing logic and so data may be held more securely in the DRAM.
The present technique seeks to improve the security of secure data stored in a DRAM.